1. Field of the Invention
The present invention relates to a camera such as a still camera used with a loaded roll film and an electronic camera with a solid-state image element, and more particularly to an improved single-lens reflex camera.
2. Description of the Related Art
Conventional still cameras have been widely used, each in which a rolled film loaded is wound up sequentially to form a camera object image on a photosensitive surface being a frame of film. Electronic still cameras are well known, each of which has a solid-state image element arranged on the photosensitive surface to record photoelectrically a camera object image.
Of the still cameras and electronic still cameras, a so-called single-lens reflex camera is known where a reflex mirror is arranged in the camera body to reflect a camera object image sent via the photographing lens to the viewfinder so that the camera object image can be visually recognized through the viewfinder.
As shown in FIG. 29, the conventional single-lens reflex camera includes a mirror 45 arranged between the photographing lens 3 and the photosensitive surface 9 on which a film is arranged, the mirror 45 being slanted at about 45.degree. with respect to the optical axis of the photographing optical system. In an observation via the viewfinder, the mirror 45 guides the light bundle irradiated from the photographing lens 3 to the viewfinder optical system formed of a field lens 21, a pentagonal Dach (or roof) prism 42, and an eyepiece 13. On photographing, the front end 45b is sprung up on the axially supported rear end of the mirror 45 (in the arrow direction shown in FIG. 29) to withdraw from the optical path of the photographing optical system so that the light bundle hits the film arranged on the photosensitive surface 9.
In the conventional single-lens reflex camera, the mirror 45 has an area substantially entirely covering the photographing surface. The mirror 45 occupies a large space between the lens 3 and the photosensitive surface 9 because the mirror 45 is arranged at a slanting angle of 45.degree. and the front end of the mirror 45 is sprung up at a photographing time to withdraw from the photographing optical system. Hence this problem causes a camera body with large thickness and a large sized photographing lens. The trend toward a large sized lens is remarkable, particularly, to the retorofocus-type wide-angle lens, and the wide-angle series and standard series zoom lenses.
The single-lens reflex camera also includes a pentagonal roof prism 44 arranged above the mirror 45 to correct the vertical and horizontal direction of an image formed by the light bundle guided to the viewfinder optical system. Hence the single-lens reflex lens camera is bulky upward. The above factors make the conventional single-lens reflex camera larger, in comparison with the separate viewfinder-type camera.
No viewfinders are superior to the single-lens reflex viewfinder in that an image itself to be photographed can be observed via the viewfinder. However, it has been considered that large-sizing the camera is avoidable in order to realize the good viewing function.
Although the single-lens reflex viewfinder is Functionally an ideal viewfinder system, the separate viewfinder built-in cameras, in each of which the viewfinder optical system is arranged separately from the photographing optical system, are generally popular among a class of amateur cameramen. The reason seems to be that the space for the mirror expands the camera body forward, thus making the size of the lens large, and the pentagonal roof prism makes the camera body bulky upward, whereby the above factors causes a large-sized camera system.
With the recent compact cameras (such as lens shutter cameras with separate viewfinders) employing zoom lenses, the zoom optical system and the drive mechanism thereof have been built in the viewfinder. Building the complicated mechanism in the narrow space degrades the fundamental function of the viewfinder, or clearness (brightness, image magnifying power, and image quality) and accuracy (visual field ratio, and parallax compensation), whereby a gap in performance between the separate-type viewfinder and the single-lens reflex viewfinder becomes larger and larger. However, it is considered that the fact that the compact cameras are the mainstream in the camera market for amateur cameramen indicates potentially that compactness is the most important factor in cameras for general amateur cameramen.
The body frame of the conventional single-lens reflex camera was structurally completed in 1932 to 1936, and the pentagonal roof prism was employed in the viewfinder in 1929 to 1950. Thus the fundamental frame structure of the single-lens reflex camera was completed in the eras. There has been a remarkable development in the performance of the single-lens reflex camera till now.
However, since the development has been built based on the fundamental frame structure completed in 1936 to 1950, the current single-lens reflex camera became larger according as development in the performance.
The efforts to miniaturize the conventional single-lens reflex camera system has been directed to various single-lens reflex camera forming elements including an integration of the pentagonal roof prism and a condenser lens and an improvement of the swinging mirror movement path. Relatively small single-lens reflex cameras appeared in the commercial market during about 10 years after 1972. However, in the 1980s the development was directed to higher performance regarding an automatic film winding mechanism, an autofocus, a zoom lens, and the like, thus leaving a miniaturization of the single-lens reflex camera behind. For a while, so-called compact cameras (separate viewfinder, lens shutter, and full-automatic function) have become the majority in the camera market. According to data issued from the Japan Camera Industrial Association in 1992, the compact cameras mark a production amount higher by about one figure than that of the single-lens reflex cameras.
There seemingly is a physical limitation to miniaturize the conventional single-lens reflex camera system as long as the camera body includes the mirror space and the pentagonal roof prism.